Adding Off-The-Shelf Memory to a Cisco 871

The Cisco 800 series routers are growing in popularity as their prices fall - but upgrades from Cisco are still outrageously above cost. As of July, a 128Mb memory upgrade was over $500 list. Fortunately with some common few-years-old commodity memory and a pair of tin snips you can upgrade your router for next to nothing.

This will, of course, void your warranty and invalidate your SmartNet contract. You have been warned.

Step 1 Find an Appropriate Dimm

The 871w can accept 168 pin, PC133 low-profile SDRam dimms with a CAS Latency of 3 or better. It can ONLY accept 64Mb or 128Mb dimms - other sizes will not work and may hose your nice router. It goes without saying but DDR won't work either. The reason Cisco still gets away with selling 128Mb sticks of ram for $500 is that the 871w requires low-profile (sometimes called half-height) RAM. Notice the picture above? Compare it to a dimm you've got lying around. The semi-circular keys on the side are only a few millimeters from the top of the module. On ordinary dimms they're in the center of the taller PCB. We're going to work our way around that limitation in the next step.

It's been a while since such memory modules were prevalent in big box stores or even from OEMs, so if you do have them it's a good idea to test that they work in a less expensive piece of hardware beforehand. A lot can go wrong with memory that's been sloshing around in a box or static bag for years.

Comments

[frollard]

Neat idea, good thing it still fits in the casing, or that could be ugly!

[Derin]

I guess you are correct.